New and need help with character controller 2d

Ok, so I'm very new to C# and Unity. My ColliderDistance2d keeps throwing the error 'cannot find type or namespace' and for Distance 'Collider2d does not contain definition for 'Distance''. I can't figure it out. It's for a tutorial and I'm not sure what I'm doing wrong. Here is the code.




using UnityEngine;


[RequireComponent(typeof(BoxCollider2D))]
public class CharController2d : MonoBehaviour
{

[SerializeField, Tooltip("Max speed, in units per second, that the character moves.")]
float speed = 9;

[SerializeField, Tooltip("Acceleration while grounded.")]
float walkAcceleration = 75;

[SerializeField, Tooltip("Acceleration while in the air.")]
float airAcceleration = 30;

[SerializeField, Tooltip("Deceleration applied when character is grounded and not attempting to move.")]
float groundDeceleration = 70;

[SerializeField, Tooltip("Max height the character will jump regardless of gravity")]
float jumpHeight = 4;

private BoxCollider2D boxCollider;


private Vector2 velocity;

private bool grounded;

private void Awake()
{
boxCollider = GetComponent<BoxCollider2D>();
}

private void Update()
{
if (grounded)
{
velocity.y = 0;

if (Input.GetButtonDown("Jump"))
{
velocity.y = Mathf.Sqrt(2 * jumpHeight * Mathf.Abs(Physics2D.gravity.y));
}
}

velocity.y += Physics2D.gravity.y * Time.deltaTime;

float moveInput = Input.GetAxisRaw("Horizontal");

float acceleration = grounded ? walkAcceleration : airAcceleration;
float deceleration = grounded ? groundDeceleration : 0;

if (moveInput != 0)
{
velocity.x = Mathf.MoveTowards(velocity.x, speed * moveInput, acceleration * Time.deltaTime);
}
else
{
velocity.x = Mathf.MoveTowards(velocity.x, 0, deceleration * Time.deltaTime);
}

transform.Translate(velocity * Time.deltaTime);

Collider2D[] hits = Physics2D.OverlapBoxAll(transform.position, boxCollider.size, 0);

grounded = false;

foreach (Collider2D hit in hits)
{
if (hit == boxCollider)
continue;

ColliderDistance2D colliderDistance = hit.Distance(boxCollider);

if (colliderDistance.isOverlapped)
{
transform.Translate(colliderDistance.pointA - colliderDistance.pointB);
}

if (Vector2.Angle(colliderDistance.normal, Vector2.up) < 90 && velocity.y < 0)
{
grounded = true;
}
}
}
}

 

You'll probably get help if you post in the scripting forum and use code tags.